When a database instance fails or shows performance issues, the Diagnostics feature analyzes its performance within a specific time range and visualizes the results to help you identify the root cause.
Prerequisites
Before you begin, ensure that:
The database instance is one of the following types:
ApsaraDB RDS for MySQL
ApsaraDB MyBase for MySQL
Self-managed MySQL database
The database instance is connected to Database Autonomy Service (DAS). For more information, see Connect a database instance to DAS.
Run a diagnostics task
Log on to the DAS console.
In the left-side navigation pane, click Instance Monitoring.
Find the database instance you want to diagnose and click its instance ID. The instance details page appears.
In the left-side navigation pane, click Diagnostics.
On the Diagnostics tab, create a diagnostics task or view historical reports.
To switch between feature versions, click Go to Old Version or Go to New Version.
FAQ
How are thread usage, connection usage, and maximum threads calculated?
These metrics apply to ApsaraDB RDS for MySQL instances and use the following formulas:
Thread usage = Number of active threads / Maximum number of threads
Connection usage = Current number of connections / Maximum number of connections allowed by the instance type
Maximum number of threads = Number of groups in a thread pool × (Number of active threads allowed per group + 1)
Why does thread usage exceed 100%?
The ApsaraDB RDS for MySQL thread pool does not limit the number of active threads. Therefore, the number of active threads may be greater than the maximum number of threads, which causes thread usage to exceed 100%.
What's next
For more information about how DAS diagnoses SQL statements automatically, see Cost-based SQL diagnostics engine.